z80

Everyone’s heard of the “black box”. Officially known as the Flight Data Recorder (FDR), it’s a mandatory piece of equipment on commercial aircraft. The FDR is instrumental in investigating incidents or crashes, and is specifically designed to survive should the aircraft be destroyed. The search for the so-called “black box” often dominates the news cycle after the loss of a commercial aircraft; as finding it will almost certainly be necessary to determine the true cause of the accident. What you probably haven’t heard of is a Quick Access Recorder (QAR).

While it’s the best known, the FDR is not the only type of recording device used in aviation. The QAR could be thought of as the non-emergency alternative to the FDR. While retrieving data from the FDR usually means the worst has happened, the QAR is specifically designed to facilitate easy and regular access to flight data for research and maintenance purposes. Its data is stored on removable media and since the QAR is not expected to survive the loss of the aircraft it isn’t physically hardened. In fact, modern aircraft often use consumer-grade technology such as Compact Flash cards and USB flash drives as storage media in their QAR.

Through the wonders of eBay, I recently acquired a vintage Penny & Giles D50761 Quick Access Recorder. This was pulled out of an aircraft which had been in service with the now defunct airline, Air Toulouse International. Let’s crack open this relatively obscure piece of equipment and see just what goes into the hardware that airlines trust to help ensure their multi-million dollar aircraft are operating in peak condition.

If you were lucky enough to own one of the crop of 1980s 8-bit computers, did you ever pause to consider how its graphics worked? Maybe the really expensive ones had dedicated CRT controller subsystems akin to the graphics cards you’d have found on a PC a few years later, but most of the affordable models would have stopped what they were doing every TV line interval period to allow access to their memory for their graphical output to be created.

The RC2014 retrocomputer dodges all this, by using a serial port as an interface and expecting your serial terminal to handle the screen. But what if it could produce its graphics directly as the machines of old did? [Rob Dobson] set out to achieve this, and not only did he succeed but he also found a way to directly emulate some classic machines along the way.

His RC2014 card which he calls the Bus Raider started as an attempt to use a Raspberry Pi to commandeer the RC2014 memory and read it via its GPIO lines, interpreting the graphics for its own screen. But even with bare metal Pi programming he couldn’t achieve the complex timing required for that, so he took an alternative approach. He ended up with an ESP32 that emulates a custom part of the RC2014 memory map and generates a display from there. Having created a custom memory map and hardware emulator for his RC2014, he then had the revelation that he could emulate any memory map, and thus he could make the retrocomputer perform natively as though it were any of a selection of classic micros. So far as well as a straight serial terminal he has a Sinclair ZX Spectrum and a Radio Shack TRS-80 running, as well as his own custom Z80 environment. And since the ESP32 also has WiFi, he can even connect to it through that medium.

Retrocomputers are something in which you might think that everything possible would already have been done, but projects like this one never cease to amaze us with their ingenuity. If you’d like to read more about the RC2014, we reviewed an earlier model back in 2016.

We feature hundreds of projects here at Hackaday, and once they have passed by our front page and disappeared into our archives we often have no opportunity to return to them and see how they developed. Sometimes of course they are one-off builds, other times they wither as their creator loses interest, but just occasionally they develop and evolve into something rather interesting.

One that is taking that final trajectory is [Just4Fun]’s Z80-MBC, a single board computer with only 4 ICs, using an Atmel microcontroller to simulate the Z80 support chips. It has appeared as a revised version, on a smart new PCB rather than its original breadboard, and with built-in SD card and RTC support through readily available breakout boards, and banked RAM for CP/M support. You may remember the original from last year, when it was also a Hackaday Prize entry and stage finalist. From a Hackaday perspective this is particularly interesting, because it shows how the Prize can help a project evolve.

The Atmega32A uses the Arduino bootloader with programming through the ICSP port, and full instructions are given in the hackaday.io project page alongside all the files required to build your own board. There is no mention of whether boards can be bought, but we’d say this could be a commercial-quality product if they chose to take it in that direction.

Faggin seems to have been at the heart of many of the early advances in microprocessors. He played a big part in the development of MOS processors during the transition from TTL to CMOS. He was co-creator of the first commercially available processor, the 4004, as well as the 8080. And he was a co-founder of Zilog, which brought out the much-loved Z80 CPU. From there he moved on to neural networking chips, image sensors, and is active today in the scientific study of consciousness. It’s time then that we had a closer look at a man who’s very core must surely be made of silicon.

Fun fact, the Osborne 1 debuted with a price tag equivalent to about $5,000 in today’s value. With a gigantic 9″ screen and twin floppy drives (for making mix tapes, right?) the real miracle of the machine was its portability, something unheard of at the time. The retrocomputing trend is to lovingly and carefully restore these old machines to their former glory, regardless of how clunky or underpowered they are by modern standards. But sometimes they can’t be saved yet it’s still possible to gut and rebuild the machine with modern hardware, like with this Raspberry Pi used to revive an Osborne 1.

Purists will turn their nose up at this one, and we admit that this one feels a little like “restoring” radios from the 30s by chucking out the original chassis and throwing in a streaming player. But [koff1979] went to a lot of effort to keep the original Osborne look and feel in the final product. We imagine that with the original guts replaced by a Pi and a small LCD display taking the place of the 80 character by 24 line CRT, the machine is less strain on the shoulder when carrying it around. (We hear the original Osborne 1 was portable in the same way that an anvil is technically portable.) The Pi runs an emulator to get the original CP/M experience; it even runs Wordstar. The tricky part about this build was making the original keyboard talk to the Pi, which was accomplished with an Arduino that translates key presses to USB.

Collecting old CPUs and firing them up again is all the rage these days, but how do you know if they will work? For many of these ICs, which ceased production decades ago, sorting the good stuff from the defective and counterfeit is a minefield.

Testing old chips is a challenge in itself. Even if you can find the right motherboard, the slim chances of escaping the effect of time on the components (in particular, capacitor and EEPROM degradation) make a reliable test setup hard to come by.

Enter [Samuel], and the Universal Chip Analyzer (UCA). Using an FPGA to emulate the motherboard, it means the experience of testing an IC takes just a matter of seconds. Why an FPGA? Microcontrollers are simply too slow to get a full speed interface to the CPU, even one from the ’80s.

So, how does it actually test? Synthesized inside the FPGA is everything the CPU needs from the motherboard to make it tick, including ROM, RAM, bus controllers, clock generation and interrupt handling. Many testing frequencies are supported (which is helpful for spotting fakes), and if connected to a computer via USB, the UCA can check power consumption, and even benchmark the chip. We can’t begin to detail the amount of thought that’s gone into the design here, from auto-detecting data bus width to the sheer amount of models supported, but you can read more technical details here.

The Mojo v3 FPGA development board was chosen as the heart of the project, featuring an ATmega32U4 and Xilinx Spartan 6 FPGA. The wily among you will have already spotted a problem – the voltage levels used by early CPUs vary greatly (as high as 15V for an Intel 4004). [Samuel]’s ingenious solution to keep the cost down is a shield for each IC family – each with its own voltage converter.

The best projects always seem to come from eBay. A few weeks ago, we found a few tiles meant for gigantic LED panel installations, and fifty bucks got you ten tiles. That eBay auction is now sold out. A while ago, [Just4Fun] realized he could build a Z80 microcomputer with $4 worth of parts from everyone’s favorite online auction house. The result is a $4 Z80 home computer, and a great Hackaday Prize entry to boot.

So, what do he need to build a retrocomputer loaded up with Forth, CP/M, and Basic? A CPU is a necessity, and [Just4Fun] found a Z80 (technically a Z84C00) for just a bit more than a dollar. A computer will need some RAM too, and a 128 kiB parallel SRAM was just the ticket for another dollar.

Here’s where things get a bit more interesting. Where the retrocomputers of yore were loaded up with glue logic, PLAs, or other weird chips, modern technology has come a long way. Instead of a massive amount of glue, [Just4Fun] is using an ATmega32A for all the I/O, address decoding, and a serial terminal.

The ATmega thrown into this cornucopia of vintage chips is itself more than a decade old, but it does have 40 pins and 32 kiB of Flash. That’s enough to ‘virtualize’ all the peripherals you’d need on a Z80 bus and provide the clock signal for the rest of the computer.

This home computer was originally designed and laid out on a solderless breadboard, but [WestfW] managed to stuff this all onto a small PCB. That’s a cheap computer that gets you all the retrocomputing goodies, and it’s something that’s just random enough to be a perfect entry for the Anything Goes portion of the Hackaday Prize.